Protein cage architectures as a nano-platform for material synthesis and metal binding
Allen, Mark Andrew
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Supramolecular proteins that assemble into cage like architectures have been used for nano-material synthesis and as a scaffold for metal binding. Material synthesis can be performed by exploiting the cage-like properties of these nano-containers and relying on the electrostatically distinct interior environment that drive mineral encapsulation. Ferritin and ferritin like proteins can be used as size constrained reaction vessels that encapsulate materials that have sizes that are determined by the internal dimensions of the protein cage. These range from 5 nm for the ferritin like protein from Listeria innocua to 24 nm for the interior of an engineered plant virus (Cowpea chlorotic mottle virus). Inorganic materials synthesized within these constrained reaction volumes are monodisperse in size. The crystallinity and phase of material prepared is determined by the reaction conditions, which are mild compared to other preparative methods.The metal binding affinity of certain viral protein cages allows the study of the role that metals play in such processes as viral assembly and infection as well as transmission. If paramagnetic metal ions are bound to the viral protein cage, the biological scaffold has potential use as an MRI contrast agent. Here multiple protein cage platforms are discussed with an emphasis on engineering non-native functionality to many of the protein cages. Engineering nonnative function to protein cages involves both genetic and chemical modification for the purpose of increasing stability and changing electrostatic interactions. Together these modifications serve to reinforce the versatility of protein cage architectures for both mineral synthesis and metal binding.